The storage of liquified gases, such as butane, propane, anhydrous ammonia and LNG, is usually in large refrigerated storage vessels. When such vessels are exposed to sudden warming, the liquid may be vaporized at a rate faster than can be relieved with the standard overpressure protection devices. The pressure relief device of the present invention is designed to protect against abnormal pressure increases in such liquified gas storage vessels.
Prior pressure relief devices of the poppet type have generally been too small to provide adequate relief for the aforementioned abnormal pressure increases. Other large diameter relief devices which were designed to rupture to provide a large relieving area have been used but the whole disc had to be replaced each time it relieved an overpressure condition, the storage tank is vented completely and such devices are difficult to accurately select their relieving pressure and are subject to handling damage and fatigue problems.
Valves have been provided which have stem guiding below the valve member, such as shown in the P. B. Drane U.S. Pat. No. 2,557,536. A suitable soft seat used in combination with a metal-to-metal seat sealing of a valve is suggested in the I. B. Weise U.S. Pat. No. 3,406,712. Tank venting for normally liquid petroleum is provided by devices such as disclosed in the F. A. Hansen U.S. Pat. No. 2,872,938.